She was aware of a sudden drop in temperature.

“I shouldn't think so,” said Carrot, slowly. “She's only nine years old.”.

One of his hands gripped her wrist tightly and the other prised the book out of her fingers.

“Hey, let go!”

“Sergeant!” shouted Carrot, over his shoulder, “can you come up here a moment?”

Angua tried to pull away. Carrot's arm was as immovable as an iron bar.

There was the creak of Colon's foot on the stair, and the door swung open.

He was holding a very small cup in a pair of tongs.

“Nobby got the coff—” he began, and stopped.

“Sergeant,” said Carrot, staring into Angua's face, “Lance-Constable Angua wants to know about Mrs Gaskin.”

“Old Leggy Gaskin's widow? She lives in Mincing Street.”

“And Mrs Scurrick?”

“In Treacle Street? Takes in laundry now.” Sergeant Colon looked from one to the other, trying to get a handle on the situation.

“Mrs Maroon?”

“That's Sergeant Maroon's widow, she sells coal in—”

“How about Annabel Curry?”

“She still goes to the Spiteful Sisters of Seven-Handed Sek Charity School, doesn't she?” Colon smiled nervously at Angua, still not sure of what was happening. “She's the daughter of Corporal Curry, but of course he was before your time—”

Angua looked up at Carrot's face. His expression was unreadable.

“They're the widows of coppers?” she said.

He nodded. “And one orphan.”

“It's a tough old life,” said Colon. “No pensions for widows, see.”

He looked from one to the other.

“Is there something wrong?” he said.

Carrot relaxed his grip, turned, slipped the book into the box, and shut the lid.

“No,” he said.

“Look, I'm sorr—” Angua began. Carrot ignored her and nodded at the sergeant.

“Give him the coffee.”

“But… fourteen dollars… that's nearly half his pay!”

Carrot picked up Vimes' limp arm and tried to prise his fist open, but even though Vimes was out cold the fingers were locked.

“I mean, half his pay!”

“I don't know what he's holding in here,” said Carrot, ignoring her. “Maybe it's a clue.”

He took the coffee and hauled up Vimes by his collar.

“You just drink this, captain,” he said, “and everything will look a lot… clearer…”

Klatchian coffee has an even bigger sobering effect than an unexpected brown envelope from the tax man. In fact, coffee enthusiasts take the precaution of getting thoroughly drunk before touching the stuff, because Klatchian coffee takes you back through sobriety and, if you're not careful, out the other side, where the mind of man should not go. The Watch was generally of the opinion that Samuel Vimes was at least two drinks under par, and needed a stiff double even to be sober.

“Careful… careful…” Carrot let a few drops dribble between Vimes' lips.

“Look, when I said—” Angua began.

“Forget it.” Carrot didn't even look round.

“I was only—”

“I said forget it.”

Vimes opened his eyes, took a look at the world, and screamed.

“Nobby!”

“Yes, sarge?”

“Did you buy the Red Desert Special or the Curly Mountain Straight?”

“Red Desert, sarge, because—”

“You could have said. Better get me—” He glanced at Vimes' grimace of horror “—half a glass of Bearhugger's. We've sent him too far the other way.”

The glass was fetched and administered. Vimes un-stiffened as it took effect.

His palm uncurled.

“Oh, my gods,” said Angua. “Have we got any bandages?”

The sky was a little white circle, high above.

“Where the hell are we, partner?” said Cuddy.

“Cave.”

“No caves under Ankh-Morpork. It's on loam.”

Cuddy had fallen about thirty feet but had cushioned the fall because he landed on Detritus' head. The troll had been sitting, surrounded by rotting woodwork, in… well… a cave. Or, Cuddy thought, as his eyes grew accustomed to the gloom, a stone-lined tunnel.

“I didn't do nothing,” said Detritus, “I just stood there, next minute, everything going past upwards.”

Cuddy reached down into the mud underfoot and brought up a piece of wood. It was very thick. It was also very rotten.

“We fell through something into something,” he said.

He ran his hand over the curved tunnel wall. “And this is good masonry. Very good.”

“How we get out?”

There was no way to climb back. The tunnel roof was much higher than Detritus.

“We walk out, I think,” said Cuddy.

He sniffed the air, which was dank. Dwarfs have a very good sense of direction underground.

“This way,” he added, setting off.

“Cuddy?”

“Yes?”

“No-one ever say there tunnels under the city. No-one know about them.”

“So…?”

“So there no way out. Because way out is way in, too, and if no-one know about tunnels, then it 'cos no way in.”

“But they've got to lead somewhere.”

“OK.”

Black mud, more or less dry, made a path at the bottom of the tunnel. There was slime on the walls, too, indicating that at some point in the recent past the tunnel had been full of water. Here and there huge patches of fungi, luminous with decay, cast a faint glow over the ancient stonework.23

Cuddy felt his spirits lift as he plodded through the darkness. Dwarfs always felt happier underground.

“Bound to find a way out,” he said.

“Right.”

“So… how come you joined the Watch, then?”

“Hah! My girl Ruby she say, you want get married, you get proper job, I not marry a troll what people say, him no good troll, him thick as a short plank of wood.” Detritus' voice echoed in the darkness. “How about you?”

“I got bored. I worked for my brother-in-law, Durance. He's got a good business making fortune rats for dwarf restaurants. But I thought, this isn't a proper job for a dwarf.”

“Sound like easy job to me.”

“I had the devil of a time getting them to swallow the fortunes.”

Cuddy stopped. A change in the air suggested a vaster tunnel up ahead.

And, indeed, the tunnel opened into the side of a much larger one. There was deep mud on the floor, in the middle of which ran a trickle of water. Cuddy fancied he heard rats, or what he hoped were rats, scuttle away into the dark emptiness. He even thought he could hear the sounds of the city—indistinct, intermingled—filtering through the earth.

“It's like a temple,” he said, and his voice boomed away into the distance.

“Writing here on wall,” said Detritus.

Cuddy peered at the letters hacked deeply into the stone.

“‘VIA CLOACA’,” he said. “Hmm. Well, now… via is an old word for street or way. Cloaca means…”

He peered into the gloom.

“This is a sewer,” he said.

“What that?”

“It's like… well, where do trolls dump their… rubbish?” said Cuddy.

“In street,” said Detritus. “Hygienic.”

“This is… an underground street just for… well, for crap,” said Cuddy. “I never knew Ankh-Morpork had them.”

“Maybe Ankh-Morpork didn't know Ankh-Morpork had them,” said Detritus.

“Right. You're right. This place is old. We're in the bowels of the earth.”

“In Ankh-Morpork even the shit have a street to itself,” said Detritus, awe and wonder in his voice. “Truly, this a land of opportunity.”

“Here's some more writing,” said Cuddy. He scraped away some slime.

“‘Cirone IV me fabricat’,” he read aloud. “He was one of the early kings, wasn't he? Hey… do you know what that means?”

“No-one's been down here since yesterday,” said Detritus.

“No! This place… this place is more than two thousand years old. We're quite probably the first people to come down here since—”

“Yesterday,” said the troll.

“Yesterday? Yesterday? What's yesterday got to do with it?”

“Footprints still fresh,” said Detritus.

He pointed.